Abstract

Velocity distributions of neutral water molecules evaporated after collision induced dissociation of protonated water clusters H+(H2O)n≤10 were measured using the combined correlated ion and neutral fragment time-of-flight (COINTOF) and velocity map imaging (VMI) techniques. As observed previously, all measured velocity distributions exhibit two contributions, with a low velocity part identified by statistical molecular dynamics (SMD) simulations as events obeying the Maxwell–Boltzmann statistics and a high velocity contribution corresponding to non-ergodic events in which energy redistribution is incomplete. In contrast to earlier studies, where the evaporation of a single molecule was probed, the present study is concerned with events involving the evaporation of up to five water molecules. In particular, we discuss here in detail the cases of two and three evaporated molecules. Evaporation of several water molecules after CID can be interpreted in general as a sequential evaporation process. In addition to the SMD calculations, a Monte Carlo (MC) based simulation was developed allowing the reconstruction of the velocity distribution produced by the evaporation of m molecules from H+(H2O)n≤10 cluster ions using the measured velocity distributions for singly evaporated molecules as the input. The observed broadening of the low-velocity part of the distributions for the evaporation of two and three molecules as compared to the width for the evaporation of a single molecule results from the cumulative recoil velocity of the successive ion residues as well as the intrinsically broader distributions for decreasingly smaller parent clusters. Further MC simulations were carried out assuming that a certain proportion of non-ergodic events is responsible for the first evaporation in such a sequential evaporation series, thereby allowing to model the entire velocity distribution.

Authors contributing to RSC publications (journal articles, books or book chapters)
do not need to formally request permission to reproduce material contained in this
article provided that the correct acknowledgement is given with the reproduced material.

Reproduced material should be attributed as follows:

For reproduction of material from NJC:
Reproduced from Ref. XX with permission from the Centre National de la Recherche
Scientifique (CNRS) and The Royal Society of Chemistry.

For reproduction of material from PCCP:
Reproduced from Ref. XX with permission from the PCCP Owner Societies.

For reproduction of material from PPS:
Reproduced from Ref. XX with permission from the European Society for Photobiology,
the European Photochemistry Association, and The Royal Society of Chemistry.

For reproduction of material from all other RSC journals and books:
Reproduced from Ref. XX with permission from The Royal Society of Chemistry.

If the material has been adapted instead of reproduced from the original RSC publication
"Reproduced from" can be substituted with "Adapted from".

In all cases the Ref. XX is the XXth reference in the list of references.

If you are the author of this article you do not need to formally request permission
to reproduce figures, diagrams etc. contained in this article in third party publications
or in a thesis or dissertation provided that the correct acknowledgement is given
with the reproduced material.

Reproduced material should be attributed as follows:

For reproduction of material from NJC:
[Original citation] - Reproduced by permission of The Royal Society of Chemistry (RSC) on behalf of the
Centre National de la Recherche Scientifique (CNRS) and the RSC

For reproduction of material from PCCP:
[Original citation] - Reproduced by permission of the PCCP Owner Societies

For reproduction of material from PPS:
[Original citation] - Reproduced by permission of The Royal Society of Chemistry (RSC) on behalf of the
European Society for Photobiology, the European Photochemistry Association, and
RSC

For reproduction of material from all other RSC journals:
[Original citation] - Reproduced by permission of The Royal Society of Chemistry

If you are the author of this article you still need to obtain permission to reproduce
the whole article in a third party publication with the exception of reproduction
of the whole article in a thesis or dissertation.

Information about reproducing material from RSC articles with different licences
is available on our Permission Requests page.